Nonwoven fabric manufactured by a prescribed process is often wound and stored in a roll form and then transported to another line, where it is unwound and fabricated into a desired product. The nonwoven fabric in roll form tends to lose its bulkiness under the winding pressure. The greater the bulkiness is, the more conspicuous this tendency becomes.
JP-A-3-220355 discloses a nonwoven fabric capable of restoring bulkiness by 5 or more fold expansion, which has constituent fibers thereof bound with a fiber binding adhesive and is restrained in a state compressed by a temporary adhesive having a melting point lower than the melting point of each of the constituent fibers and the fiber binding adhesive. The nonwoven fabric restores its bulkiness upon being heated at a temperature equal to or higher than the melting point of the temporary adhesive and lower than the melting point of each of the constituent fibers and the fiber binding adhesive. JP-A-4-142922 discloses a material capable of increasing bulkiness, which contains a compressed nonwoven fabric capable of increasing in thickness upon being heated and a sheet material, wherein the compressed nonwoven fabric and the sheet material are joined with an adhesive. The compressed nonwoven fabric is a bulky nonwoven fabric having been compressed into a thinner fabric and held in the compressed state by thermally fusible fibers or low-melting resin particles. On being heated by dry heat or wet heat, the bonds by the thermally fusible fibers or low-melting resin particles in the compressed nonwoven fabric loosen to allow the constituent fibers to restore its bulkiness by its own restoring force. The above-described nonwoven fabrics are intentionally made to reduce its bulkiness by using a temporary adhesive, thermally fusible fibers or low-melting resin particles in order to facilitate sewing or like fabrication steps of the nonwoven fabric. Hence, the techniques disclosed have no direct relation to the reduction in bulkiness due to winding pressure.
JP-A-6-158499 proposes a process of producing nonwoven fabric, in which a fiber aggregate containing thermally bonding fibers having a low-melting component and a high-melting component is subjected to heat treatment followed by a cooling treatment to bond the thermally bonding fibers. In this process, the fiber aggregate is heated with hot air at or above the melting point of the low-melting component blown at a velocity of 0.2 to 5 m/sec for 0.1 to 300 seconds and, immediately thereafter, cooled with a low temperature gas (−30 to 45° C.) blown at such a low velocity as to apply no flow pressure, i.e., a velocity of 0.1 to 1 m/sec for 0.1 second or longer, thereby solidifying the low-melting component. This technique is to address the problem of bulkiness reduction caused by blowing low-temperature gas in the nonwoven fabric manufacturing and therefore has no direct relation to the reduction of bulkiness due to winding pressure.